Self regulating pumps in particular for the injection of fuel into internal combustion engines



Feb. 4, 1964 P. E. BESSIERE 3,120,189

SELF REGULATI NG PUMPS IN PARTICULAR FOR THE INJECTION I 0F FUEL INTOINTERNAL COMBUSTION ENGINES Original Filed Dec. 15, 1958 v 2Sheets-Sheet 1 ATTORRIEYS 5 Feb. 4, 1964 P. E. BESSIERE 3,120,189

SELF REGULATING PUMPS IN PARTICULAR FOR THE INJECTION OF FUEL INTOINTERNAL COMBUSTION ENGINES Original Filed Dec. 15, 1958 2 Sheets-Sheet2 BY gox miw AT7'ORNEKS United States Patent Ofifiee 3,l2fi,l9 PatentedFeb. 4, 1964 3,120,189 SELF REGULATKNG PUMPS 1N PARTICULAR FQR THEINJEtZTiGN @F FUEL INTO INTERNAL QGMBUSTHQN ENGENES Pierre EtienneBossier-e, Neuiily-sur-Seine, France, as-

siguor to Societe Anonyme pour lEsploitatiou des Procedes Chi nes etPhysiques, Zug, Switzerland, 2 Swiss company Continuation of applicationher. No. 7559, 352, Dec, 15, 1953. This application May 22, 1962, Set.No. 19$,7d2 Claims priority, application France Dec. 23, 1957 9 Claims.(Cl. ll)34l) The present invention relates to self-regulating pumps andin particular to pumps for the injection of fuel into internalcombustion engines.

The pumps with which my invention is concerned inelude a dischargeconduit the opening of which prevents the pump from delivering liquid,this discharge conduit being controlled by valve means urged byresilient means toward discharge conduit closing position and actuatedto open this discharge conduit by a control fiuid receiving, owing tothe provision of a throttled passage in the ircuit through which saidcontrol fluid is flowing, pressure impulses at a frequency equal to thatof the reciprocating movement of the pump piston, the maxrnium pressurereached by this control fluid during every impulse and preferably therate of increase of the fluid pressure during each of said impulsesbeing the higher as this frequency is lr'gher until said maximum fluidpressure is capable of overcoming the action of said resilient means andof opening said discharge conduit.

The object of my invention is to provide a pump of this type which isbetter adapted to meet the requirements of practice than those used upto the present time.

For this purpose, according to my invention, I provide means for brakingthe return displacements of said valve means from discharge conduitopening position t ward discharge conduit closing position so thatreturn displacements take place at a rate independent of the frequencyof reciprocation of said piston per unit of time and such that, for highvalues of said frequency, said discharge conduit is open during thewhole of every compression stroke of said piston.

A preferred embodiment of the present invention will be hereinafterdescribed with reference to the accompanying drawings, given merely byway of example and inwhich:

FIGS. 1 and 2 diagrammatically show, in axial section, a fuel injectionpump made according to the present in- Vention, the parts being shown intwo relative difierent positions in said figures respectivel The pumpshown by the drawings includes a piston 1 driven in such manner, forinstance by means or" a cam (not shown), that the movement of the pistonis accelerated from the time, at the beginning of its upward stroke,when fuel starts being compressed and delivered. When the upward strokeof piston 1 is obtained by means of a cam, the downward stroke thereofis obtained by means of a return spring 2.

Piston 1 reciprocates in a cylinder 3 into which opens, at 4a, a feedconduit 4 through which fuel arrives in the usual manner from anauxiliary pump (not shown).

Furthermore, a delivery conduit 5 provided with a checkvalve 6 leads outfrom said cylinder 3. This delivery conduit 5 conveys the fuel deliveredby the pump toward the injector or injectors (not shown) of the enginefed by the pump.

A discharge conduit 7 also leads from the top cylinder 3 to the outside.This discharge conduit '7 is controlled by a moving element 8 consistingfor instance of a slide valve.

Piston 1, during its upward stroke and after it has closed port 4a,delivers fuel into conduit 5 as long as slide valve t5 keeps dischargeconduit 7 closed. But fuel delivery through conduit 5 ceases as soon asslide valve 8 opens discharge conduit 7.

In order to control slide valve 3, l apply thereto, on the one hand adownwardly directed force preferably produced by a return spring 9, forinstance adjustable by means of a screw it, and on the other hand theupwardly directed thrust of a fluid (and in particular a liquid)receiving pressure impulses at a frequency equal to that of thereciprocating move. rent of piston 1, this pressure reaching, during theupward strokes of piston 1, peak values which increase, as the speed atwhich the pump is driven (i.e.) (the speed of the engine fed by thepump) increases up to a value for which said pressure overcomes theresistance of spring 9. Then, for speed exceeding this value, the liquidpressure capable of overcoming the resistance of spring 9 is reached forshorter upward displacements of piston 1.

In order to produce said pulsating pressure of the liquid used toactuate slide valve 13, I make use of an auxiliary reciprocating pumpincluding an auxiliary piston 11 fitting slidably in an auxiliarycylinder 12. Cylinder 12 is provided with a feed conduit 13, alsopreferably connected with the delivery of a primary pump (not shown)which may be the same as that which supplies liquid to conduit 4. Adelivery conduit 14, leading from auxiliary cylinder 12. and containinga check-valve 15', is in communication 'ith one or the ends 33 of a cylnder 16 in which slide valve 53 is slidably fitted, the pressure of theliquid in conduit 14 acting against the thrust of return spring 9 onslide valve 8.

According to a particularly simple construction illustrated by thedrawing, the main piston 1 and the auxiliary piston 13, form a singleunit and cylinders 3 and 12 are in line and coaxial with each other. Inthis case, return spring 2 may be housed in cylinder 12, this springbeing common to both of the pistons Ill and 1, which are driven by thesame earn. Feed conduits 4 and 13 are disposed in such manner as to besimultaneously closed by pistons l and 11 respectively, so that thecompression strokes of said pistons begin simu-=.aneously.

In order to comply with the above stated conditions concerning thepressure of the liquid delivered by piston 11, this liquid is caused topass through a throttled passage controlled by slide valve 8 itself. Anoutlet conduit l7 branching out from conduit 14, for instance from theportion 14a thereof located downstream of cylinder 16, opens into thewall of cylinder 16 opposite a discharge conduit 17a in line withconduit 1'7. Slide valve 8 is provided with a groove 19 located at alevel such that, when slide valve 8 is in its position of rest (wherethe bottom end of said valve is applied against an abutment 2%} as shownby FIG. 1), the lower edge of groove 19 and the opening of conduit 17into cylinder 16 limit between them a throttled passage 21 through whichthe liquid delivered by piston Ill must flow to pass into dischargecouduit 17a.

The initial value of the cross-section of this throttled passage dependsupon the position of abutment 20, which position is preferablyadjustable by means of a screw 22.

It will be seen that as soon as the pressure of the liquid delivered bypiston 11 reaches a value sufilcient to overcome the thrust of returnspring 9, the area of the crossseetion of throttled passage 21decreases, and quickly becomes equal to zero. If, at this time, piston11 has not yet reached the end of its upwardstrolte, slide valve 8 issuddenly pushed upward until a second groove 23, provided in slide valve3 below groove 19, comes opposite conduits 1'7 and 17a and thus enablesthe liquid still delivered by piston 11 to flow to the outside. Thismovement or" slide valve 8 simultaneously brings opposite dischargeconduit 7 a third groove 24 provided in slide valve 8 above groove 19,whereby conduit 7 places cylinder 3 in communication with the outside Inorder to obtain the return of slide valve 8 to its position of restimmediately after the beginning of every downward stroke of pistons 11and 1, the portion 14a of delivery conduit 14 is placed incommunication, during every downward stroke of piston 11, with adischarge conduit 14b by-passing throttled passage 21, this conduit 1411being of course closed during every upward (delivery) stroke of piston11.

In order to control this discharge conduit 1%, I advantageously make useof a slide valve 25 actuated in synchronism with the reciprocatingmovement of piston 11 by means of the pressure of the liquid present incylinder 12. 7 For this purpose, one of the ends of cylinder 26, inwhich slide valve 25 is movable, is connected through a conduit 27 tocylinder 12, or delivery conduit 14. In this last case, which is thatillustrated by the drawings, the point of conduit 14 fromwhich conduit27 branches out is located upstream of check-valve 15. A return spring28 interposed between the upper end of cylinder 26 and slide valve 25urges said slide valve toward its position of rest where it is appliedagainst a shoulder 29 at the lower end of cylinder 26. In this positionof rest, slide valve 25 opens, through its groove 3%, the communicationbetween conduit Ida and discharge conduit 1411. Thus, slide valve 25 isin its position of rest during every downward stroke of piston 11 and itis moved away from its position, thus closing the communication withdischarge conduit 14b, during every upward stroke of piston 11.

In the embodiment of my invention shown by the drawings, conduits 4 and13 open into the respective cylinders 3 and 12 at points such that,during every upward stroke of pistons 1 and 13, piston 11 closes conduit13 and starts compressing liquid and delivering it from cylinder 12 atthe same time as piston 1 closes conduit 4 and delivers liquid fromcylinder 3 toward delivery conduit 5. Discharge. conduit 14:; isthrottled at 31 and the crosssection of this throttled portion ofconduit 1% is advantageously adjustable by means of a screw 32 the endof which projects more or less into conduit 14:; to form said throttledportion.

Groove 24 is of a height much greater than that of discharge conduit 7.Furthermore groove 23 is positioned in slide valve 3 so as to opendischarge conduit 1717a and thus to stop the upward movement of slidevalve 8 when said slide valve has moved a substantial distance beyondthe position for which its groove 24 starts opening discharge conduit 7.

FIG. 1 shows the parts in the position they occupy when pistons 1 and 11are approximately in their lower dead center position.

This pump works as follows.

Since pistons 11 and 1 are supposed to undergo an acceleration, duringevery upward stroke thereof, even when the engine on which the pump ismounted runs at a constant speed, the pressure of the liquid which,during every upward stroke of piston 11, flows through the throttledpassage 21, rises during said stroke up to a value which, as long asslide valve 8 is not lifted, is. for relatively low values of the speedof the engine on which the pump is mounted, increases when said speedincreases. For a given value of the engine speed, this liquid pressure,which acts upon the lower end face of slide valve 8, becomessufiiciently high to overcome the resistance of spring 9 and slide valve8 starts moving upwardly. This movement further reduces thecross-section area of throttled passage 21 which, in turn, increases theliquid pressure acting on the lower end face of valve 8 and furtheraccelerates the reduction of the cross-section area of throttled passage21. Full closing of throttled passage 21 and upward displacement ofslide valve 8 to the position where it opens discharge conduit 7 aretherefore practically instantaneous. Slide valve 8 then remains in itsupper position (FIG. 2) until the end of the upward stroke of piston 11,groove 23 opening the communication between conduits 1'7, 17a by anamount just sufficient to keep it in this position.

For higher and higher speeds of the engine above the above mentionedvalue, this opening of discharge conduit 7 takes place for shorter andshorter upward strokes of piston 11. As long as the opening of dischargeconduit 7 takes place after inlet conduit 4 has been closed by piston 1,some amount of fuel is delivered by piston 1 through delivery conduit 5toward the injector or injectors to be fed by the pump but this amountdecreases as the speed of the engine (i.e. the frequency ofreciprocation of pistons 1 and 11) increases.

Furthermore, during the return (downward) movements of slide valve 8(which then discharges the liquid present in chamber 16 through conduit14b, slide valve 2 5 having been pushed into lower position by spring28), the flow of liquid is slowed down by the throttling of said conduit14!; at 31, thus braking said downward movements of slide valve 8. For agiven throttling at Hand a given adjustment of spring 9, the time takenby slide valve to move down from its upper position (shown by FIG. 2) toa bottom position in which groove 19. opens passage 21 between 17 and17a is always the same, irrespective of the speed at which the pump isdriven. Therefore, as this speed increases, it reaches a value such thatpiston 11 begins its compression (upward) stroke before slide valve 8has had time to reach this bottom position. The liquid pressure thensupplied by piston 11 quickly returns slide valve 8 into the positionwhere discharge conduit 7 is fully opened. Injection is then reduced toa minimum. If the engine speed has reached a value such that piston 11starts on'its upward stroke before slide valve 8 has begun to shut offdischarge conduit 7, said discharge conduit remains constantly open.There is no longer any injection and a limit speed has been reached.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and eflicient embodiments of my invention,it should be well under stood that I do not wish to be limited theretoas there might be changes made in the arrangements, disposition and formof the parts without departing from the principle of the presentinvention as comprehended within the scope of the accompanying claims.

This application is a continuation of my prior application Ser. No.780,452, filed December 15, 1958, for Improvements in Self RegulatingPumps in Particular for the Injection of Fuel Into Internal CombustionEngines, now abandoned.

What I claim is: r

1. A pump which comprises, in combination, a pump body forming acylinder, a piston fitting slidably in said cylinder and having areciprocating movement therein, a

liquid delivery conduit leading from one end of said cylinder, so thatliquid can be delivered from said cy1inder through said delivery conduitduring the compression strokes of said piston, feed conduit meansopening into said cylinder for filling said cylinder with liquid during,the suction strokes of said piston, a discharge conduit lead-- ing fromsaid cylinder and opening to the outside thereof, a valve casing mountedin fixed position on a portion of said "discharge conduit, a valve insaid casing to control, the discharge of liquid from said cylinder tothe outside thereof through said discharge conduit, whereby opening ofsaid discharge conduit by said valve during a compression stroke of saidpiston prevents the delivery of liquid through said delivery conduit,resilient means operatively connected with said valve for constantlyurging it toward discharge conduit closing position, said valve casingand said valve limiting between them a variable Volume chamber such thatexpansion of the volume thereof urges said valve toward dischargeconduit opening position, a fluid control circuit full of fluid andwholly distinct from said delivery conduit and said discharge conduit,said fluid control circuit having an inlet and a throttled passageopening to the outside, said control circuit being in communication withsaid casing so that it includes said variable volume charnber, meansoperatively connected with said piston and in communication with saidcontrol circuit inlet for periodically applying fluid pressure impulsesto the fluid in said control circuit at a frequency equal to thefrequency of reciprocation of said piston so that the maximum fluidpressure during every impulse increases as said frequency increases,whereby, for a given value of said frequency, said maximum fluidpressure becomes capable of overcoming the action of said resilientmeans and of bringing said valve into discharge conduit openingposition, said means for applying pressure fluid impulses beingoperatively connected with said piston in such manner as to start eachof said pressure impulses with a given constant phase relation withrespect to the beginning of the corresponding compression stroke of saidpiston, an outflow conduit wholly distinct from said delivery conduitand said discharge conduit and in communication with said chamber topermit escape of fluid therefrom during the displacements of said valvefrom discharge conduit opening position toward discharge conduit closingposition and 2a throttled passage in said outflow conduit to brake saidlast mentioned valve displacements so that they take place at a rateindependent of said frequency of reciprocation of said piston.

2. A pump which comprises, in combination, a pump body formin acylinder, a piston fitting slidably in said cylinder and having areciprocating movement therein, a liquid delivery conduit leading fromone end of said cylinder, so liquid can be delivered from said cylinderthrough said delivery conduit during the compression strokes of saidpiston, f ed conduit means opem'ng into said cylinder for filling saidcylinder with liquid during he suction strokes of said piston, adischarge conduit leading from said cylinder and opening to the outsidethereof, a valve casing mounted in fixed position on a portion of saiddischarge conduit, a valve in said casing to control the discharge ofliquid from sm'd cylinder to the outside thereof through said dischargeconduit, whereby opening of said discharge conduit by said valve duringa compression stroke of said piston prevents the delivery of liquidthrough said delivery conduit, resilient rneans operatively connectedwith said valve for constantly urging it toward discharge conduitclosing position, said valve casing and said vdve limiting between thema variable volume chamber such that expansion of the volume thereofurges said valve toward discharge conduit opening position, a fluidcontrol circuit full of fidl and wholly distinct from said deliveryconduit and said discharge conduit, said fluid control circuit having aninlet and a throttled passage opening to the outside, said controlcircuit being in communication with said casing so that it includes saidvariable volume chamber, means operatively connected with said pistonand in communication with said control circuit inlet for periodicallyapplying fluid pressure impulses to the fluid in said control circuit ata frequency equal to the frequency of reciprocation of said piston sothat the rate of increase of the fluid pressure during every fluidpressure impulse is the higher as said frequency is higher and that themaximum fluid pressure during every impulse increases as said frequencyincreases, whereby, for a given value of said frequency said maximumfluid pressure becomes capable of overcoming the action of saidresilient means and of bringing said valve into discharge conduitopening position, said means for applying pressure fluid impulses beingoperatively connected with said piston in such manner as to start eachof said pressure impulses with a given constant phase relation withrespect to the beginning of the corresponding compression stroke of saidpiston, an outflow conduit wholly distinct from said delivery conduitand said discharge conduit and in communication with said chamber topermit escape of fluid therefrom during the displacements of said valvefrom discharge conduit opening position toward discharge conduit closingposition and a throttled passage in said outflow conduit to brake saidlast mentioned displacements so that they take place at a rateindependent of said frequency of reciprocation of said piston.

3. A pump which comprises, in combination, a cylinder, a piston fittingslidably in said cylinder and having a reciprocating movement therein, aliquid delivery conduit leading from one end of said cylinder, so thatliquid can be delivered from said cylinder through said delivery conduitduring the compression strokes of said piston, feed conduit meansopening into said cylinder for filling said cylinder with liquid duringthe suction strokes of said piston, a discharge conduit leading fromsaid end of said cylinder and opening to the outside thereof, acylindrical casing transverse to said discharge conduit and intersectingit so that a length of said discharge conduit consists of a portion ofsaid casing, a slide valve fitting sl-idably in said cylindrical casingand movable therein to control the discharge of liquid from saidcylinder to the outside thereof through said discharge conduit, wherebyopening of said discharge conduit by said slide valve during acompression stroke of said piston prevents the delivery of liquidthrough said delivery conduit, resilient means interposed between saidslide valve and said casing for constantly urging said slide valvetoward discharge conduit closing position, one end of said cylindricalcasing forming a. chamber such that expansion thereof causes said slidevalve to move toward discharge conduit opening position, meansoperatively connected with said piston for feeding 'nto said chamber,during every compression stroke of said piston, fluid at a flow rateconstantly increasing for a time, the rate of increase of said flow ratebeing the higher as the number of reciprocations of said piston per unitof time is higher, an outlet conduit leading from said chamher andhaving a length thereof constituted by a portion of said casing, saidslide valve being provided with a. groove arranged to cooperate withsaid outlet conduit and to clear it partly, when said slide valve is inthe position where the volume of said chamber is minimum, to such adegree that expansion of the volume of said chamber causes a reductionof the cross-section area of said outlet conduit thus cleared by saidgroove, said slide valve being provided with another groove, arranged toclear said outlet conduit when said slide valve is in discharge conduitopening position, whereby said fluid can then be discharged to theoutside through said outlet conduit, said casing being so dimensionedthat, for a given value of said frequency of reciprocation of saidpiston, the fluid fed into said chamber reaches a pressure capable ofovercoming the action of that resilient means and of bringing said slidevalve into discharge conduit opening position, an outflow conduit incommunication with said chamber to permit escape of fluid therefromduring the return displacements of said slide valve from dischargeconduit opening position toward discharge conduit closing position and athrottled passage in said outflow conduit to rake said returndisplacements so that they take place at a rate independent of thenumber of reciprocations of said piston per unit of time.

4. A pump according to claim 1 further including valve means in saidoutflow conduit operatively connected with said piston for closing saidoutflow conduit during the compression strokes of said piston andopening said outflow conduit during the return strokes of said piston.

5. A pump according to claim 1 further including means carried by saidcasing for adjusting said resilient means.

6. A pump accordin to claim 1 further including means carried by saidcasing for adjusting the limit position toward which said slide valve isurged by said resilient means.

7. A pump according to claim 1 in which said means for feeding fluidinto said chamber include a cylinder coaxial with said first mentionedcylinder and in fixed position with respect thereto, a piston rigid withsaid first mentioned piston and fitting slid-ably in said secondmentioned cylinder and feed conduit means opening into said secondmentioned cylinder and positioned so that the compression strokes ofboth of said pistons occur simultaneously, said pump further including aconduit leading from said second mentioned cylinder to said chamber, anda check valve in said last mentioned conduit mounted to open only towardsaid chamber.

8. A pump which comprises, in combination, a pump body forming acylinder, a piston fitting slidably in said cylinder and having areciprocating movement therein, a

liquid delivery conduit leading from one end of said cyl-' inder, sothat liquid can be delivered from said cylinder through said deliveryconduit during the compression strok s of said piston, feed conduitmeans opening into said cylinder for filling said cylinder with liquidduring the suction strokes of said piston, a discharge conduit leadingfrom said cylinder and opening to the outside thereof, a valve casingmounted in fixed position on a portion of said discharge conduit, avalve in said casing to control the discharge of liquid from saidcylinder to the outside thereof through said discharge conduit, where byopening of said discharge conduit by said valve during a compressionstroke of said piston prevents the delivery 7 of liquid through saiddelivery conduit, said valve being so arranged that, when it is movedvfrom its discharge conduit closing position in the direction to opensaid discharge conduit, it can move well beyond the position where itfirst opens said discharge conduit while leaving said discharge conduitopen, as far as a position which will be called discharge conduit finalopening position, resilient mean-s operatively connected with said valvefor constantly urging it toward discharge conduit closing position, saidvalve casing and said valve limiting between them a variable volumechamber such that expansion of the volume thereof urges said valvetoward discharge conduit opening position, a fluid control circuit fullof fluid and wholly distinct from said delivery conduit and saiddischarge conduit, said fluid control circuit having an inlet and athrottled passage opening to the outside, said control circuit being incommunication With said casing so that it includes said variable volumechamber, means operatively connected with said piston and incommunication with said control circuit inlet for periodically applyingfluid pressure impulses to the fluid in said control circuit at afrequency equal to the frequency of reciprocation of said piston so thatthe maximum fluid pressure during every impulse increase as saidfrequency increases, whereby, for a given value of said iretuuancy saidmaximum fluid pressure becomes capable of overcoming the action of saidresilient means and or" bringing said valve into discharge conduit finalopening position, said means for applying pressure fluid impulses beingoperatively connected with said piston in such manner as to start eachof said pressure impulses with a given constant phase relation withrespect to the beginning of the corresponding compression stroke of saidpiston, an outflow conduit Wholly distinct from said delivery conduitand said discharge conduit and in communication with said chamber topermit escape of fluid therefrom during the displacements of said valvefrom discharge conduit opening posit-ion toward discharge conduitclosing position and a throttled passage in said outflow conduit tobrake said last mentioned valve displacements so that they take place ata rate independent of said frequency of reciprocation of said piston,whereby for high values of said frequency, said discharge conduit isopen during the whole or every compression stroke of said position.

9. A pump according to claim 8 wherein said valve is a slide valveprovided with an annular groove in its intermediate portio-n so thatsaid dischargeconduit is opened when a portion of said groove is locatedopposite said discharge conduit, the height of said groove being atleast twice the diameter of said discharge conduit.

References ited in the file of this patent UNITED STATES PATENTS FranceFeb, 16, 1959

1. A PUMP WHICH COMPRISES, IN COMBINATION, A PUMP BODY FORMING ACYLINDER, A PISTON FITTING SLIDABLY IN SAID CYLINDER AND HAVING ARECIPROCATING MOVEMENT THEREIN, A LIQUID DELIVERY CONDUIT LEADING FROMONE END OF SAID CYLINDER, SO THAT LIQUID CAN BE DELIVERED FROM SAIDCYLINDER THROUGH SAID DELIVERY CONDUIT DURING THE COMPRESSION STROKES OFSAID PISTON, FEED CONDUIT MEANS OPENING INTO SAID CYLINDER FOR FILLINGSAID CYLINDER WITH LIQUID DURING THE SUCTION STROKES OF SAID PISTON, ADISCHARGE CONDUIT LEADING FROM SAID CYLINDER AND OPENING TO THE OUTSIDETHEREOF, A VALVE CASING MOUNTED IN FIXED POSITION ON A PORTION OF SAIDDISCHARGE CONDUIT, A VALVE IN SAID CASING TO CONTROL THE DISCHARGE OFLIQUID FROM SAID CYLINDER TO THE OUTSIDE THEREOF THROUGH SAID DISCHARGECONDUIT, WHEREBY OPENING OF SAID DISCHARGE CONDUIT BY SAID VALVE DURINGA COMPRESSION STROKE OF SAID PISTON PREVENTS THE DELIVERY OF LIQUIDTHROUGH SAID DELIVERY CONDUIT, RESILIENT MEANS OPERATIVELY CONNECTEDWITH SAID VALVE FOR CONSTANTLY URGING IT TOWARD DISCHARGE CONDUITCLOSING POSITION, SAID VALVE CASING AND SAID VALVE LIMITING BETWEEN THEMA VARIABLE VOLUME CHAMBER SUCH THAT EXPANSION OF THE VOLUME THEREOFURGES SAID VALVE TOWARD DISCHARGE CONDUIT OPENING POSITION, A FLUIDCONTROL CIRCUIT FULL OF FLUID AND WHOLLY DISTINCT FROM SAID DELIVERYCONDUIT AND SAID DISCHARGE CONDUIT, SAID FLUID CONTROL CIRCUIT HAVING ANINLET AND A THROTTLED PASSAGE OPENING TO THE OUTSIDE, SAID CONTROLCIRCUIT BEING IN COMMUNICATION WITH SAID CASING SO THAT IT INCLUDES SAIDVARIABLE VOLUME CHAMBER, MEANS OPERATIVELY CONNECTED WITH SAID PISTONAND IN COMMUNICATION WITH SAID CONTROL CIRCUIT INLET FOR PERIODICALLYAPPLYING FLUID PRESSURE IMPULSES TO THE FLUID IN SAID CONTROL CIRCUIT ATA FREQUENCY EQUAL TO THE FREQUENCY OF RECIPROCATION OF SAID PISTON SOTHAT THE MAXIMUM FLUID PRESSURE DURING EVERY IMPULSE INCREASES AS SAIDFREQUENCY INCREASES, WHEREBY, FOR A GIVEN VALUE OF SAID FREQUENCY, SAIDMAXIMUM FLUID PRESSURE BECOMES CAPABLE OF OVERCOMING THE ACTION OF SAIDRESILIENT MEANS AND OF BRINGING SAID VALVE INTO DISCHARGE CONDUITOPENING POSITION, SAID MEANS FOR APPLYING PRESSURE FLUID IMPULSES BEINGOPERATIVELY CONNECTED WITH SAID PISTON IN SUCH MANNER AS TO START EACHOF SAID PRESSURE IMPULSES WITH A GIVEN CONSTANT PHASE RELATION WITHRESPECT TO THE BEGINNING OF THE CORRESPONDING COMPRESSION STROKE OF SAIDPISTON, AN OUTFLOW CONDUIT WHOLLY DISTINCT FROM SAID DELIVERY CONDUITAND SAID DISCHARGE CONDUIT AND IN COMMUNICATION WITH SAID CHAMBER TOPERMIT ESCAPE OF FLUID THEREFROM DURING THE DISPLACEMENTS OF SAID VALVEFROM DISCHARGE CONDUIT OPENING POSITION TOWARD DISCHARGE CONDUIT CLOSINGPOSITION AND A THROTTLED PASSAGE IN SAID OUTFLOW CONDUIT TO BRAKE SAIDLAST MENTIONED VALVE DISPLACEMENTS SO THAT THEY TAKE PLACE AT A RATEINDEPENDENT OF SAID FREQUENCY OF RECIPROCATION OF SAID PISTON.